不同截面形式混凝土梁桥的竖向温度梯度效应分析

为分析不同规范中混凝土梁桥竖向温度梯度模式的差异,评估竖向温度梯度效应对混凝土梁桥的影响程度,总结了不同国家和行业规范中混凝土梁桥的竖向温度梯度模式,从梯度曲线形式和温度基数取值两方面讨论了效应计算结果的差异。选取了20多座不同结构体系、跨径和截面形式的混凝土梁桥,计算了在包括桥梁变形和截面应力在内的2种典型的竖向正温度梯度作用下的各项效应,与自重和汽车作用产生的效应作了对比。结果表明:不同规范的竖向温度梯度模式在梯度曲线形式和温度基数取值方面存在显著差异,它们对温度效应计算结果具有同等程度的影响; 顶部温差的影响深度越大,桥梁的变形和次生弯矩越大,考虑底部升温段时截面下缘有更大的自压应力; 不同的铺装层类型和气候条件造成桥梁温度基数取值存在差异,进而导致温度效应可能相差1.5倍～2.0倍; 相同结构体系和截面形式的中小跨混凝土梁桥随着跨径增大,自重效应占比增加,汽车和温度效应占比减小,但是温度和汽车效应的相对比例基本保持不变; 结构体系和跨径相同时,T梁的温度效应占比要比空心板和小箱梁高出0.6%～16.5%; 温度效应在一些效应类型中占有很大比例,温度作用引起的中小跨简支梁桥的变形和截面上缘应力能与自重和汽车效应相近,引起的中小跨连续梁桥的截面上缘应力能超过自重和汽车效应甚至两者总和,墩顶截面下缘应力能与自重和汽车效应相当,引起的大跨径连续箱梁桥截面上缘应力能超过汽车效应的数倍; 若考虑铺装层类型和气候条件的影响,在温度基数取值较大的梁桥上,温度效应占比可能更高。

Analysis of Vertical Temperature Gradient Effects of Concrete Girder Bridges with Different Cross Sections

In order to analyze the difference of vertical temperature gradient patterns of concrete girder bridge in different specifications and evaluate the influence degree of vertical temperature gradient effect on concrete girder bridge, the vertical temperature gradient patterns of concrete girder bridge in different national and industrial codes were summarized. The differences of the effect calculation results were discussed from the gradient curve form and the temperature base values. More than 20 concrete girder bridges with different structural systems, spans and cross sections were selected to calculate the effect under two typical vertical positive temperature gradients, including the deformation of the bridge and the stresses in the section. The temperature effects were compared with the effect induced by the self-weight and the vehicle loads. The results show that there are significant differences in the form of gradient curve and the base value of temperature in different vertical temperature gradient patterns, which equally influence the calculation results of temperature effect calculation results. The greater the influence depth of the top temperature difference is, the greater the deformation and secondary bending moment of the bridge, and the greater the self-equilibrium pressure stress is at the bottom edge of the section when the bottom heating part is considered. Different pavement types and climate conditions lead to different temperature base values in bridges, which may lead to a 1.5-2.0 times difference of temperature effects. For the middle and small span concrete girder bridges with same structural system and cross section, the proportions of self-weight effect increase, and the proportions of vehicle and temperature effect decrease with the increase of span, but the relative proportions of temperature and vehicle effects basically remain unchanged. The temperature effect proportions of T-girders are higher than that of hollow slab and small-box girder with the same structural system and span, which are 0.6%-16.5%. The temperature effect accounts for a large proportion of some effect types. The deformation of the girder and the stress on the top edge of the section in the middle and small span simple-supported concrete girder bridge caused by the temperature effect are equivalent to that of the self-weight and vehicle effect. The stresses on the top edge of the section in the middle and small span continuous girder bridge caused by temperature gradient can exceed that of the self-weight and vehicle effect, or even the sum of them, and the stress on the bottom edge of the section at the pier can be equivalent to that of the self-weight and vehicle effect. The temperature stresses on the top edge of the long-span continuous box girder bridge are several times bigger than that induced by vehicle effect. Considering the influences of pavement type and climate condition, the proportion of temperature effect may be higher in the bridge with larger temperature base value.